A study carried out at the National Institute of Environmental Health Sciences has established that men with increased body mass index (BMI) are significantly more likely to be infertile than normal-weight men. Lead researcher, Markku Sallmen, said that for every 20 pounds of excess weight a man carried, the chance of infertility increased by about 10 percent.

"Women who are overweight tend to have a more difficult time becoming pregnant than normal-weight women," explained researcher Donna Baird, who added that this was the first study to establish that weight was also a factor in male fertility.

The study, which has just been published in the journal Epidemiology, found that male BMI was an independent risk factor for infertility; irrespective of age, cigarette smoking, alcohol intake and solvent or pesticide exposure. Incredibly, there was nearly a 2-fold increase in the chance of infertility among men defined as obese.

Somewhat annoyingly, the researchers did not have data on the subjects' frequency of sexual intercourse, so it's possible that overweight men might actually have less sexual intercourse than their normal-weight counterparts, and this could influence the fertility results. But the researchers say this is unlikely as recent studies looking at semen characteristics show lower semen quality for overweight and obese men, as well as hormonal differences.

Based on material from the National Institute of Environmental Health Sciences